"...stock valvetrain with 067 cam..."
Next step up would be the Melling SPC-7, which is supposed to be close to the 068 Pontiac.
If you wanna stay with near .400 lift, the Melling SPC-3 is said to be similar to the 744 Pontiac cam, but tamer. That #1028 cam looks to have the same specs as the SPC-3. This list has some good cam specs.
http://www.pontiacpower.org/PontiacCams.htm
If .454 lift is not more than you want, the Lunati 10510312 might work for you.
https://www.lunatipower.com/street-m...8-276-286.html
Then if you don't mind changing to stronger springs, there are lots of higher lift choices.